Access method for data packet networks

ABSTRACT

This invention relates to optical communications and is designed for use in data transmission networks.  
     The technical effect of this invention consists in lowering capital and operating costs per unit of information transmitted and at the same time raising the overall maximum access speed. Subsidiary technical effects include allowing various groups of users to be organized at different service levels within a single service sector by using different electromagnetic radiation beams (including a single wavelength), and also enhancing security against unauthorized access.  
     The method comprises extracting data packets addressed to the subscribers of a subscriber access point from the network and transmitting the information contained in these packets by a directional electromagnetic radiation beam. The beam is directed at the receiving devices of subscribers at their respective addresses. The claimed method is used to transmit information to subscribers by optical-range electromagnetic radiation while dynamically controlling the spatial characteristics of the electromagnetic radiation beam using the address information of the packets so that the radiation beam is directed to the receiving device of a respective subscriber during transmission of a particular data packet. This embodiment of the invention uses an electromagnetic radiation beam of narrow angular divergence and the direction of its propagation is varied dynamically. In another embodiment of the invention, the spatial characteristics of the beam are controlled by a dynamic hologram that is, for each registered subscriber address, an optical match of the aforesaid electromagnetic radiation source and the receiver of the subscriber at that address. 1 independent claim and 2 dependent claims, 2 illustrations.

FIELD OF THE INVENTION

[0001] This invention relates to optical communications and is designedfor use in data transmission networks.

PRIOR STATE OF THE ART

[0002] Known in the art are methods of organizing systems allowingsubscribers to access data transmission networks based on fiber opticscommunication systems (see, for example, Russian Patent No. 2,127,489,IPC H04B 10/12).

[0003] Prior art methods of organizing systems to give subscribersaccess to a data transmission network provide for extracting packets(cells) containing the addresses of subscribers being served from thenetwork, converting the signals and transmitting them in fiber opticscables connecting the respective optical receivers and transmitters onthe side of the access point and on the subscriber side. A majordrawback of such methods is high installation and operation costs of afiber optics communication line that place it beyond the reach ofordinary subscribers.

[0004] The closest prior art of the present invention in technical ideais a method of organizing access to packet data transmission networkswherein a data packets addressed to subscribers of a subscriber accesspoint are extracted from the network and the information contained inthe data packets is transmitted by an electromagnetic radiation beamthat is directed to the receiving devices of subscribers at respectiveaddresses (Communication World-Connect, No. 7, 2000, pp. 93-94, inRussian).

[0005] An example of a prior art method, or prototype, is provided bythe Alcatel 9900 system (ibid.). This is a wireless access systemoperating within the microwave range of 24.25 to 29.5 GHz. The basestation (subscriber access point) has a standard ATM network interfaceand is adapted to extract data packets addressed to the subscribers ofthis access point from the data stream. All the subscribers of a stationare allocated to four service sectors combined into a circle diagram.The subscriber data packets corresponding to a particular sector areused, together with the ATM addresses combined with the subscriber codesfor modulating the electromagnetic radiation beam emitted by adirectional transmitting antenna serving a respective sector. Thesubscriber devices filter data addressed to specified subscribers fromthe overall information stream transmitted by a single electromagneticradiation beam to the sector as a whole.

[0006] The most serious drawbacks of this method are its low speed andrelatively low cost-effectiveness of data transmission.

[0007] This invention is designed to raise the speed andcost-effectiveness of data transmission and to simultaneously expand thefunctional possibilities of the access system.

[0008] The technical effect that can be achieved by performing thismethod consists in lowering capital and operating costs per unit ofinformation transmitted and at the same time in raising the overallmaximum access speed. Subsidiary technical effects include allowingvarious groups of users to be organized at different service levelswithin a single service sector by using different electromagneticradiation beams (including a single wavelength), and also enhancingsecurity against unauthorized access.

[0009] To attain this objective and achieve the above technical effectin the prior art method of organizing access to packet data transmissionnetworks, wherein data packets addressed to subscribers of a subscriberaccess point are extracted from the network and the informationcontained in the data packets is transmitted by an electromagneticradiation beam directed at the receiving devices of subscribers at therespective addresses, according to this invention uses optical-rangeelectromagnetic radiation is used to transmit information tosubscribers, and the spatial characteristics of the electromagneticradiation beam are controlled using the address information of the datapackets so that, during transmission of a particular data packet, theradiation beam is directed at the receiving device of a respectivesubscriber.

[0010] Other embodiments of this method can be used, wherein it isadvisable to:

[0011] use an electromagnetic radiation beam of a narrow angulardivergence and dynamically vary the direction of its propagation; and

[0012] control the spatial characteristics of the beam by a dynamichologram that is, for each registered subscriber address, an opticalmatch of the aforesaid electromagnetic radiation beam and the inputwindow of the subscriber's receiver at that address.

ESSENCE OF THE INVENTION

[0013] The essence of this invention and its subsidiary embodiments isexplained below with reference to drawings that illustratediagrammatically the various embodiments of the access system organizedin accordance with the method of this invention. The drawings and thefollowing text do not clarify a method of transmitting information fromsubscribers to an access point, because this method is not essential forachieving the expected positive effect.

[0014]FIG. 1 shows a possible structural diagram of an access systemaccording to the method disclosed herein on the basis of an embodimentusing an electromagnetic radiation beam of narrow angular divergence.

[0015]FIG. 1 shows diagrammatically data transmission network 1, device2 providing access to data transmission network, modulator 3,electromagnetic radiation source 4, device 5 to deflect anelectromagnetic radiation beam, subscriber terminals 6, and subscriberreceiving devices, or antennas 7.

[0016] Data transmission network 1 is accessed through access device 2.Device 2 extracts data packets addressed to the subscribers of aparticular service sector from the information stream and the packetsare directed at modulator 3. Radiation from laser 4 (or another narrowangular divergence source) is modulated in this embodiment by varyingthe optical power thereof with the aid of modulator 3, even thoughsources directly modulating any specific parameters of anelectromagnetic radiation beam can be used. Information about theaddress of data packet, used at a particular moment for beam modulation,is transmitted, prior to the start of the beam modulation cycle, to adeflecting device (deflector) 5. Deflector 5 is used to alter thedirection in which the electromagnetic beam is propagated by directingit, during transmission of the packet addressed to a particularsubscriber 6, to the subscriber's receiving device 7.

[0017]FIG. 2 illustrates another embodiment of the method describedherein. FIG. 2 shows a diagrammatic view of data transmission network 1,device 2 providing access to the data transmission network, directlymodulated electromagnetic radiation source 3, dynamic hologram formingdevice 4, and subscriber terminals 5 with receiving devices (antennas)6.

[0018] In this particular auxiliary embodiment of the claimed method,data transmission network 1 is also accessed through access device 2.Data packets addressed to subscribers of a particular service sector areextracted from the information streams and used for modulating theradiation of the source 3. Optical power (or another parameter) ofelectromagnetic radiation from the source 3 is modulated directly byinformation contained in the data packet transmitted to a particularsubscriber, and the address information is used for forming dynamicholograms in device 4. Holograms are actually diffraction lattices (flator three-dimensional according to the method by which they are formed indevice 4), which are used to focus radiation from source 3 on receivingdevice 6 of subscriber 5 at a respective address during datatransmission to the subscriber.

[0019] In contrast to the prior art method and other similar methods,the use of optical frequency range in combination with address controlof an electromagnetic radiation beam during data packet transmissionallows transmission speed to be increased in orders (in proportion tothe ratio of the radio frequency used previously to the optical rangefrequency) and lowering the power required per subscriber. Besides,capital and operating costs per unit of information transmitted arereduced accordingly. It also becomes possible to deploy several (two ormore) systems within a single physical service sector (the same area) toprovide access to the same or other transmission networks at the sameoptical frequency, including services provided at different levels ofquality. Addressed direction of an information-carrying electromagneticradiation beam (in fact, data packets transmitted themselves) helps toenhance security of transmission against unauthorized access.

[0020] The use of this method (and its subsidiary embodiments),therefore, allows the claimed task to be fulfilled and the expectedtechnical effect achieved.

INDUSTRIAL APPLICABILITY

[0021] The claimed invention can be used extensively in datatransmission networks to provide data transmission to different groupsof users at different service levels within a single service sector byusing different electromagnetic radiation beams.

1. A method of organizing access to packet data transmission networks,wherein data packets addressed to subscribers of a subscriber accesspoint are extracted from the network and the information contained inthe data packets is transmitted by an electromagnetic beam that isdirected at the receiving devices of subscribers at respectiveaddresses, characterized in that, in order to raise the speed andcost-effectiveness of data transmission and simultaneously to expand thefunctional possibilities of the access system, information istransmitted to subscribers by electromagnetic optical-range radiation,while dynamically controlling the spatial characteristics of theelectromagnetic radiation beam using packet address information so thatthe radiation beam is directed at the receiving device of a respectivesubscriber during transmission of a particular data packet.
 2. A methodas claimed in claim 1, characterized in that the electromagneticradiation beam used therein has a narrow angular divergence and thedirection of propagation thereof is varied dynamically.
 3. A method asclaimed in claim 1, characterized in that the spatial characteristics ofthe beam are controlled by a dynamic hologram that is, for eachregistered subscriber address, an optical match of the source of theaforesaid electromagnetic radiation beam and the receiver of thesubscriber at that address.